Overview
Folate is a one-carbon donor vitamin; serum folate reflects recent intake, RBC folate longer-term stores.
Clinical Importance
Macrocytic anemia workups with B12
Deficiency assessment
Specimen Requirements
- Specimen: serum or lithium heparin plasma (method- and analyzer-dependent; follow the performing laboratory)
- Tube: gold/SST (serum separator) or green-top lithium heparin as validated locally
- Handling: invert gently; allow SST to clot fully before centrifugation; separate promptly
- Storage: refrigerate serum/plasma if testing is delayed per analyte stability limits
- Stability: analyte-specific; do not exceed institutional or manufacturer time/temperature limits
- Fasting: follow institutional/protocol fasting requirements when the ordered pathway requires fasting
Analytical Method
Competitive immunoassays; protect from light.
Instruments Used
Automated analyzers
- Roche Cobas chemistry and immunoassay systems
- Abbott Alinity / Architect chemistry and immunoassay systems
- Siemens Healthineers Atellica / ADVIA chemistry and immunoassay systems
- Beckman Coulter AU / DxC chemistry systems
- Beckman Coulter Access / DxI immunoassay systems
- Mindray BS-series chemistry analyzers
- Ortho Clinical Diagnostics Vitros systems
- Thermo Fisher / Indiko and related chemistry platforms
- Randox clinical chemistry systems
Manual methods
- Manual immunoassay methods in selected settings
Reference Values
Typical adult SI examples below follow widely published international clinical chemistry practice (e.g., Tietz; Henry's). Always interpret against the method- and demographics-specific interval printed on the patient report (CLSI EP28-A3c). Neonatal, pediatric, pregnancy, and assay-generation intervals differ.
Method-specific; serum folate often roughly >7–10 nmol/L (>3–4 ng/mL) as adequacy thresholds depending on method; use local interval.
Interpretation
Common Causes of Increased Results
- High folate; supplementation
Common Causes of Decreased Results
- Low folate; deficiency
Clinical Significance
- Deficiency and anemia panels
Factors Affecting Results
Pre-analytical
- Light exposure; recent meal effects on serum folate
Analytical
- Calibration/QC failure; reagent lot shifts
- Carryover or substrate depletion on high-throughput analyzers
- Assay-specific interference (heterophile antibodies for immunoassays)
Post-analytical
- Using serum folate alone when RBC folate is indicated
Advantages and Limitations
Advantages
- Paired with B12 for macrocytosis
Limitations
- Serum folate is intake-sensitive
Clinical Pearls
Always pair folate with B12 in macrocytic anemia; treating folate alone can mask B12 neuropathy risk.
References
Authoritative textbooks, guidelines, and reviews supporting this laboratory test reference. Verify reference intervals, critical limits, and method details against institutional protocols and current guideline editions.
Textbooks
- Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 8th ed. Elsevier; 2022.
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
- Bishop ML, Fody EP, Schoeff LE. Clinical Chemistry: Principles, Techniques, and Correlations. 9th ed. Jones & Bartlett; 2022.
CLSI and Professional Guidelines
- International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Recommendations and reference measurement systems for clinical chemistry measurands (verify current IFCC documents for the analyte).
- Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
- Clinical and Laboratory Standards Institute. Collection of Diagnostic Venous Blood Specimens. CLSI standard GP41. CLSI.
- American Diabetes Association. Standards of Care in Diabetes. Diabetes Care (annual update).
- Kidney Disease: Improving Global Outcomes (KDIGO). Clinical Practice Guideline for Evaluation and Management of Chronic Kidney Disease.
- American Association for the Study of Liver Diseases (AASLD). Practice guidance related to evaluation of abnormal liver chemistries / liver disease laboratory evaluation (verify current AASLD publication and institutional adoption).
Frequently Asked Questions
Common questions about using this Folate laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.
What is the Folate laboratory test reference used for?
This Medical Laboratory Library page summarizes the clinical importance of Folate. Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.
Where can I find Folate specimen requirements?
See the Specimen Requirements section on this page for specimen information related to Folate. Confirm collection details against your laboratory protocol.
Where are Folate reference values listed?
See the Reference Values section on this Laboratory Library page. Reference ranges can vary by method and population, so verify intervals with your laboratory.
How do I interpret Folate results?
Use the Interpretation section for laboratory interpretation framing, including increased and decreased result patterns when provided. Do not treat educational text as a patient-specific diagnosis.
What analytical method is used for Folate?
See the Analytical Method section for principle and method notes. Method details may differ by instrument and institutional SOP.
Are related laboratory tests linked from Folate?
Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.
How can I continue learning after reading Folate?
Use Continue learning links on this page for related Academy lessons, medical laboratory quizzes, or laboratory case studies when available for this Clinical Chemistry topic.
What are the clinical pearls for Folate?
See the Clinical Pearls section for concise laboratory practice notes associated with Folate. Apply pearls alongside institutional protocols.
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